The subject matter of the present disclosure relates to illumination arts, lighting arts, solid-state lighting arts, and related arts.
Various types of incandescent lamps (e.g., integral incandescent lamps and halogen lamps) mate with a lamp socket via a threaded base connector (sometimes referred to as an “Edison base” in the context of an incandescent light bulb), a bayonet-type base connector (e.g., a bayonet base in the case of an incandescent light bulb), or other standard base connector. These lamps often form a unitary package, which includes components to operate from standard electrical power (e.g., 110 V and/or 220 V AC and/or 12 VDC). In the case of incandescent and halogen lamps, these components are minimal, as the lamp comprises an incandescent filament that operates at high temperature and efficiently radiates excess heat into the ambient. Many incandescent lamps are omni-directional light sources. These types of lamps provide light of substantially uniform optical intensity distribution (or, “intensity distribution”). Such lamps find diverse applications such as in desk lamps, table lamps, decorative lamps, chandeliers, ceiling fixtures, and other applications where a uniform distribution of light in all directions is desired.
Developments in lamp and lighting technology continue to introduce solid-state devices to generate light. The performance of solid-state lighting technologies (e.g., light-emitting diode (LED) devices) is often superior to incandescent and halogen lamps in terms of, for example, useful lifetime (e.g., lumen maintenance and reliability over time) and higher efficacy (e.g., Lumens per Electrical Watt (LPW)). Whereas the lifetime of incandescent lamps is typically in the range of about 1000 to 5000 hours, lighting devices that use LED devices can operate in excess of 25,000 hours, and perhaps as much as 100,000 hours or more. In terms of efficacy, incandescent and halogen lamps are typically in the range of 10-30 LPW, while lamps with LED devices can have efficacy of 40-100 LPW with anticipated improvements that will raise efficacy even higher in the future.
Unfortunately, many LED devices are typically highly directional by nature. Common LED chips are flat and emit light from only one side. Thus, although superior in performance, many commercially-available LED lamps cannot achieve the uniform distribution found in conventional lamps. In some applications, the requirement for 40, 60, 75 and 100 watt equivalent LED lamps to replace conventional incandescent lamps specifies that the lamp must generate light with uniform intensity from 0-135 degrees in the latitude direction.
Moreover, lamps that use solid-state technology must be equipped to adequately dissipate heat. LED devices are highly temperature-sensitive in both performance and reliability as compared with incandescent or halogen filaments. These sensitivities are often addressed by placing a heat sink in contact, or in thermal contact, with the LED device. However, the heat sink may block light that the LED device emits and hence further limits the ability to generate light of uniform intensity distribution. Physical constraints such as regulatory limits that define maximum dimensions for all lamp components, including light sources, further limit that ability to properly dissipate heat.